FIELD OF THE INVENTION
The invention relates to a rotary printing machine with a device for treating the surface of sheets and, more particularly, to a sheet-fed rotary printing machine having a delivery wherein at least one drier for varnish or printing ink is provided. In such rotary printing machines, conveying elements, such as chain conveyors or transfer drums, for example, which have grippers assembled thereon, are provided in the delivery, and have thermal drying devices, cooling devices, powdering devices or redampening devices assigned thereto for treating the surface of the sheets. The printed surface of the sheets are prevented thereby from smearing or smudging, and the sheets are prevented from sticking to one another.
At high machine speeds, in order to achieve the desired effect, it is necessary to employ a large amount of energy in the treatment of the surface and for the energy-active stage to have dimensions which are as large as possible. Heretofore known devices for treating the surface of the sheets have therefore require a great amount of space. For example, the construction shown in the published German Patent Document DE 66 03 661 U1 requires a relatively great erection height in order to accommodate vertically arranged chain conveyors. For a web-fed printing machine having a modular construction, the published European Patent Document WO 95/29813 A1 provides, for each module, a drier which is assigned to a web length running rectilinearly in a vertical direction.
In the construction shown in German Patent 688,935, a drying drum with a large circumference is used, the dry air serving for the drying being also effective during the rotation of the drum. The dwell time of the fresh printing ink in the drying air may be further lengthened if the diameter of the drying drum is increased in size. In addition to the large volume which has to be provided for the drying drum, a disadvantage arises in that the print on the surface of the sheets is damaged by resting on screen-like supporting elements. The supporting elements impair the effectiveness of the drying air supplied. Moreover, the provision of a co-rotating drier device is complicated from a construction standpoint.